In a N-color printer (N≧4), the image profiling process constructs a lookup table (LUT) from a device-independent colorimetric color space (for example, sRGB space) to the device color space (for example, CMYK) based on the characteristics of the target printer. Each node in the table corresponds to a 3-to-N mapping. Therefore, there is N-3 degree of freedom in determining the mapping for each input color, which can be exploited to optimize image quality related objectives. Traditionally, the smoothness of LUT in the device color space is the main constraint in deriving the profile. This is necessary to reduce the separation noise to avoid artifacts such as contours in the prints. Existing profiling algorithms manually adjust the gray color replacement (GCR) level along the neutral axis to achieve desired performance, which can be time consuming and may not yield optimal results when several cost functions are taken into consideration.
Accordingly, what is needed in this art are increasingly sophisticated methods for profile LUT construction which, while ensuring the smoothness of LUT in the device color space and robust color match, improve one or more image quality attributes of the resulting prints.